Conventional frying processes are carried out with heated cooking oil, in which food items are immersed, exposed to air. This results in deterioration of the quality and appearance of the oil due to constant oxidation of the oil by air. The quality of the fried food may be spoiled by partially oxidized oil, and consumption of the fried food can pose a health hazard.
During the frying process, oil penetrates into the food items being fried. After the food items are removed from the oil, oil adhered to the surface of the fried items may be removed by shaking or centrifugation, or by subjecting the items to a hot air-jet. Removing cooking oil from the surface of the food items, however, leaves substantial amounts of oil in the interior of the food items. The oil present in the food items adds to the caloric content of the food items.
U.S. Pat. No. 5,263,406 to Chiu discloses a system for frying food in a frying tank that is partially filled with hot oil. Food items are introduced into thee frying tank above the oil. The frying tank is then hermetically sealed and air in the frying tank is removed to create a vacuum over the oil of about 60 torrs. The food items are then immersed in the hot oil. The frying oil is circulated in a closed system which maintains the temperature of the oil and filters the oil. After frying the fried food items are removed from the oil and shaken in the vacuum for deoiling.